This invention relates to a device and method for non-invasively controlling human and animal hearts in a manner that treats emergency arrhythmias of the cardiac atrium.
Atrial arrhythmias are abnormal electrical contraction (beating) of the two thin-walled atrial chambers. The two smaller atrial chambers of the heart sit atop the two thick-walled large ventricular chambers. Those powerful ventricular chambers pump blood both to the lungs (right ventricle) and to the entire body (left ventricle). Atrial chambers have the job of pumping blood downwardly to fill the two ventricles before they contract (pump).
Arrhythmias (irregular beating or fibrillation) of atrial chambers can lead to serious performance deficit in the ventricles. Ventricles that receive less than adequate level of blood begin to contract (pump) at ever increasing rates per minute. Ventricles speed up because sensory information processed in the brain indicates that inadequate blood circulation is happening (i.e., inadequate oxygen being supplied). When heart beat cycles become too fast the heart can go into fibrillation which further cuts the oxygen supply and eventually leads to mortality.
Fibrillation is an exceedingly rapid, but disorganized, contraction or twitching of the heart muscle fibril electrical system that causes grossly inefficient contraction of the heart muscle (myocardium). Especially in the atrial chambers the twitching is vermicular (or wormlike) and tends to evolve into rapid circular electrical activation rather than the more normal slower linear conduction. Further understanding of heart fibrillation is that it is recurrent, involuntary and abnormal that prevents normal contraction (pumping action) to circulate blood. The heart muscle (myocardium) quivers during fibrillation and blood circulation falls off severely. The normally coordinated electrical contraction of the myocardium degrades to chaotic electrical conduction which seemly cannot correct itself without critical medicinal and/or electrical intervention.
Prompt treatment is the best way to return the heart to a normal rhythm. Patients usually receive treatment for atrial fibrillation in hospital emergency rooms. Since it takes time to arrive in the emergency room, patients often are in deteriorating medical condition. If there were a simple treatment that could be applied by the patient or a paramedic which tended to lower ventricular heart rate and take atria out of fibrillation the condition of the patient arriving at the emergency room would be better.
When atrial fibrillation (sometimes called A-fib) occurs in the atrial chambers a quivering caused by very fast circular wave-forms occurs within the thin cardiac muscles that make up the wall of the two chambers. The normal beat rate of about 80 beats per minute (bpm) can now rise to 400–500 BPM. Such fast, but weak beats, “churn” the blood and may cause blood-clots which can break-off and travel to the brain, causing a significant stroke risk.
Fibrillating atrial chambers are inefficient at pumping blood. As A-fib proceeds it retards blood circulation and impairs the entire body. Atrial fibrillation starves the ventricles for adequate blood supply. When the atrium are unable to supply adequate blood to the ventricles, then the entire body becomes endangered by insufficient oxygenation. Oxygen is carried by the blood's red cells and is transported by arteries to serve the entire body. In addition, an impaired returning venous blood circulation causes insufficient removal of waste products from all the organs and cells. Patients feel as if they are suffocating because of oxygen starvation so providing oxygen “early” is an important part of treatment.
The longer atrial fibrillation proceeds unchecked, the more likely death will occur. This dangerous process begins when blood does not fill the ventricles. In response, the brain instructs the ventricles to pump faster because not enough blood is circulating. Since the ventricles are pumping with only partially filled chambers bio-alarms go off in the brain and the patient begins having feelings of impending doom. The patient in atrial fibrillation becomes anxious at the prospect of death as his ventricles accelerate their beat. Patients in such extremis are most often unable to do anything to help themselves and faint or collapse, and in a sense, are witness to their own death. If the patient had a simple treatment device it might be possible to reverse a potentially lethal outcome.
Atrium(s) which are fibrillating certainly are weakly pumping ever more insufficient blood to the ventricles. Hence the cardiac ventricles respond by gradually beating (pumping) faster and faster (tachycardia) trying to reach hydrodynamic balance. The atrium could be beating at 400 to 500 bpm and the ventricles at something like 150 to 180 bpm. Such powerful and rapid ventricular beats are felt in one's pulse and often as chest palpitations (irregularly or regular pounding heart). Since normal pulse is in the range of 60 to 90 for a resting human, it becomes alarming at 180 bpm. During fibrillation, the electrical system of the heart is disorganized, erratic and the normal rhythmic beat is lost. Most atrial fibrillation terminates spontaneously or is converted to a normal rhythm in a hospital emergency room. However, if the A-fib continues on, it can deteriorate by effecting the two ventricular chambers of the heart, as previously described.
Life threatening events begin to occur as ventricles join in the emergency. Breathing becomes more difficult with beginning feelings of suffocation. Often the patient becomes dizzy, faints or collapses. Patients may complain of chest pain or heart palpitations, if they are conscious. Once the racing ventricles decay to around 200 bpm they can begin mortally fibrillating. Each passing minute of total heart fibrillation is 10% of death. In 6 or 7 minutes brain damage is occurring and by 10 minutes the patient is indeed dead. So a fibrillating atrial event, in time, will decay to ventricular fibrillation and lead to certain death, unless corrected.
If the patient can arrive at the hospital emergency room before ventricular crisis happens there are two modes of treatment. One treatment is to use high-voltage electrical defibrillation paddles to try and convert the arrhythmia(s) to normal fibrillation. A second treatment is to use certain calcium antagonists medications such as Diltiazem or Verapamil to slow down the conduction circuits.
However, the medication technique must be done early in the atrial fibrillation since effectiveness usually takes a period of time, even hours, to return the heart to normal rhythm. Once the patient is stabilized other treatments include burning out conductive circuits in the atrial muscle with lasers or ultrasound to limit its ability to conduct in certain areas. This treatment can fail if it destroys critical elements of the atrial circuitry and potentially requires emergency implantation of a heart pacemaker to save the patient.
The atrium can have other rhythm disturbances that also require medical treatment. One of these is called “flutter.” When this occurs, the patient says, “it feels like a bird is in my chest flapping its wings!” This is an appropriate and exacting description. Breathing is somewhat labored (breathlessness) and the condition can occur as alternating flutter and A-fib, called “fib-flutter.” Flutter consists of slower beat rates of about 200 to 300 bpm within the atrium. Flutter is usually treated with medications to convert back to normal rhythm. Flutter alone is usually more of a nuisance to a patient since hemodynamic compromise usually does not occur. Still other disturbances include chaotic and multifocal atrial tachycardia which also can decay into fibrillation. In addition there is totally unexpected paroxysmal fibrillation of a sudden onset, with intermittent rapid and irregular atrial rhythm due to multiple reentrant electrical wavelets in the atrial contractile muscle.
Atrial fibrillation can also be sustained at beat rates of about 350 bpm or lower down to 120 bpm and is refractory to treatment. Such fibrillation can go on for hours or even days without mortality. Such patient may have recurrent attacks of A-fib often without endangering hemodynamics of the ventricles. These patients, as time goes on, often must have a pacemaker implanted to prevent a mortal event during one of their A-Fib episodes. The main risk is embolic (tendency to form clots), and hence anticoagulation is needed. If an embolus (clot) forms it can be the precursor of a dangerous stroke. Otherwise, clotting prevention is approached by having patients take an aspirin every day or a prescribed blood-thinner, if they have a potential of having recurrent fibrillation attacks. The atrium otherwise can contact (beat) with poor muscle tone or pump too fast or slow requiring a medication program or pacemaker implantation.
There is little most patients can do to treat atrial fibrillation events outside the hospital emergency room. There are more than 2,000,000 people in the United States that experience A-Fib annually. When this happens the patient is rushed to an emergency room for treatment. It is best to treat A-Fib the moment after it starts, since conversion back to normal heart rhythm can then occur more easily. As it runs on, the hemodynamics and the brain's reaction to events, deteriorate the patient's medical condition with time.
Once the aberrant rhythm goes on for a while it becomes intrenched and more difficult to convert. Safe, rapid treatment by the patients themselves would be most productive. If patients still requires hospitalization they would likely be in better condition from self-treatment than if they did nothing and were transported in an ambulance which would provide only oxygen and hook-up an EKG to monitor cardiac status.
The vagus nerve in the case of atrial fibrillation treatment is actually the out put of “efferent” nerve. The carotid artery bifraction (where the artery splits the blood suppy into two arterial pathways) contains two sensors that we are stimulating. They are the carotid sinus and the carotid body which have sensory nerves that lead to the medulla oblongata with instructions. Afferent nerve is an input informational nerve that provides information to the medulla to help it select the appropriate out put signal that travels, in this case, to the heart.
The vagus nerve contains both afferent and efferent nerves in its bundle. There are some 100,000 fibers in the vagus. About 75% of the fibers are afferent sensors. The balance are the output efferent nerves that travel to all the internal organs that keep the body alive.
The present invention is designed to stimulate nerves leading to circuits that would calm aberrant rhythms in the heart and offer an immediate treatment modality for patients in their homes or businesses and by paramedics.